Our invention relates to a jackknifing-affecting apparatus for an articulated vehicle, in particular for so-called push-type articulated busses having electronic sensing and control units; moreover our invention is an electronic control and sensing device for said jackknifing-affecting apparatus and force and moment exerting units of said construction that can be hydraulically or mechanically operated wherein or a combined operation is also possible. Our invention also relates to an electronic device for sensing and evaluating the angular position of two turning elements, i.e. a sensor for sensing the angular position with outputs for the digital angle-signal and control signal respectively.
There are several propositions known from patent specifications for preventing jackknifing of articulated busses, that is, articulated vehicles consisting of several members. According to our knowledge, the device described in the West German Patent DE-PS No. 2 420 203 has been most widely applied in the way of practical realization.
In said apparatus four hydraulic working cylinders--arranged between the two members of the vehicle--represent the force and moment exerting elements and the common hydraulic valve unit thereof is controlled by an electronic control unit. The electronic control unit receives one of the input signals from the potentiometer sensing the angular displacement of the steered wheels of the first member of the vehicle, while the other input signal arrives from the potentiometer sensing the angle of articulation of the two members of the vehicle. The electronic microcomputer continuously compares the effective value of angle of articulation with the value of articulation ordered to the prevailing angle of the steered wheel and stored in the memory and upon reaching the permitted angle of articulation the output signal closes said two working cylinders on one side via the valve unit and prevents overarticulation in this direction. Operational safety depends fully on the reliability of the sensor with the potentiometer, of the signal forwarding lines and the electronic unit. Faultless condition of the electronic unit may be controlled by the apparatus in such a manner that upon starting the motor of the vehicle a fixed test program is allowed to run repeatedly and in case of identical results a faultless condition will be indicated. Everywhere two sensors each with potentiometers are built-in and two alarming signal lamps are provided for the driver that the apparatus could meet the requirements relating to safe operation and signalling demanded during the operation of the vehicle. The mechanical part and hydraulical cylinders of the apparatus are built-in so as to prevent, by blocking, the development of the angle of articulation at the steered front wheel which would surpass the angle of articulation in direction of the angle of articulation belonging thereto, at the same time, in case of the change of the angle of articulation in the opposite direction no influence will be exerted until reaching the angle of articulation of 0.degree., thereafter velocity of turning will be damped only, however, blocking against turning will not be performed.
The solution having been described in the Hungarian patent application (AU-428) corresponding to the patent U.S. Pat. No. 4,344,640 and to the published West German Patent Application No. 30 31 601.9 has no such disadvantageous properties; the device described here resists any change of the angle of articulation in any extraordinary direction. The embodiment is hydromechanically operated, with cams, with sensors matching thereto, and a difference-forming unit containing a spring-element.
Both with the aforementioned electronically controlled apparatus and the latter hydromechanical apparatus a predetermined angle of articulation is ordered for the existing steered angle of the wheel, wherein with a vehicle continuously driven on a circular path this angle of articulation is calculated and programmed into the control unit of the apparatus, assuming a slipfree rolling of the wheels.
Both with electronic control and hydromechanical solution the difference-forming comparator of the control unit is working with the highest accuracy, at the same time certain negligance is to be allowed in the course of determining the angle of articulation belonging to the steered angle of the wheel, on the other hand an articulated vehicle travelling on a public way almost never travels on a circular path with a constant radius, if only because of the lateral creeping of the tires having been influenced by dynamic forces. Accordingly, it can be stated that in practice the presently used apparatuses, i.e. the control units thereof are superfluously accurate and as a consequence a tolerance-band is to be used, the case of surpassing said band the control unit is giving the order for the actuation of force exerting elements. Although an apparatus with reduced accuracy would suffice for performing the task of control, this must not go to the debit of reliability, as faulty function of the apparatus for the prevention of jackknifing may result in severe accidents.